(CCU and cables) to the monitor [1–5, 13, 17].
A major milestone toward the goal of higher image definition, using image enhancement technology, was attained with the marketing of HD television (HDTV) camera systems. The ongoing process in this huge consumer technology sector has led to a variety of 3D endoscope systems culminating in the introduction of Ultra HD systems providing the 4K standard (Figure 3.8b) with a horizontal screen display resolution of approximately 4000 pixels as opposed to 1080 with full HD.
Over the last decade, various methods and technologies to enhance contrast, and early detection of mucosal and submucosal lesions, were described and used in clinical practice. These include autofluorescence (AF), conventional chromoendoscopy (CC), and recently enhanced contact endoscopy (ECE). These technologies were developed because white light endoscopic routine evaluation might fail to identify early‐stage lesions in epithelial or subepithelial layers, or to detect accurate margins in macroscopic lesions.
ECE is based on the dynamic fusion of the conventional IEE (image‐enhanced endoscopy) with CE (contact endoscopy) – but without the need for vital staining – and thus combines the advantages of both modalities.
Currently, imaging technologies that provide detailed contrast enhancement of the mucosa and blood vessels are widely used in many human medical specialties. The major focus of current research and development in the field of endoscopic imaging technologies is on the advancement of image‐enhanced endoscopy (IEE) systems (i‐SCAN, NBI, and IMAGE1 STM). The IMAGE 1 STM (KARL STORZ Tuttlingen, Germany) is a versatile digital full HD video system, providing specific color rendering of the acquired broad visible spectrum within the HD‐camera system. Since spectral separation is obtained within the camera system and amplified by adapted color processing algorithms, the IMAGE 1 STM does not require a dedicated narrow band light source and operates with a standard light source using the whole spectrum of light information. Therefore, this system enhances the appearance of the mucosal surface structures and subepithelial vasculature by selected wavelengths of light providing five different predefined spectral ranges in addition to the standard mode with white light: CLARA, CLARA + CHROMA, CHROMA, SPECTRA A, SPECTRA B. The KARL STORZ IMAGE 1 S system was awarded the Innovation of the Year by EAES – European Association for Endoscopic Surgery, in 2014 when the product was introduced, becoming a standard since then, for modern laparoscopic and thoracoscopic surgery.
ECE is currently used in small animal endoscopy (i.e. gastrointestinal, respiratory, and urinary systems) and MIS (laparoscopy and thoracoscopy). Enhancement of different vascular patterns, surface contrast, and elimination of edge shadowing allow surgical procedures to be performed with higher levels of accuracy compared to previous standard video imaging systems [18, 19].
Fluorescence is the property in which certain molecules (fluorochromes) emit fluorescent radiation when excited by a laser beam or exposed to near‐infrared light (NIR) at specific wavelengths. Once the light energy is absorbed by the fluorochrome's organic molecules, an excitation of delocalized electrons from ground state to a higher energy level occurs. Upon return from the excited singlet state to the ground state, energy is emitted in the form of photons, reaching the observer's eye as fluorescence of a specific wavelength.
Fluorescence image‐guided surgery (FIGS) is a medical imaging technique that uses fluorescence to detect properly labeled structures during surgery. Its purpose is to guide the surgical procedure and provide the surgeon a real‐time view of the operating field. When compared to other medical imaging modalities, FIGS is cheaper and superior in terms of resolution and number of molecules detectable. As a drawback, penetration depth is usually very poor (100 microns) in the visible wavelengths, but it can reach up to 1–2 cm when excitation wavelengths in the near infrared are used. FIGS is performed using imaging devices with the purpose of providing real‐time simultaneous information from color reflectance images (bright field) and fluorescence emission. One or more light sources are used to excite and illuminate the sample. Light is collected using optical filters that match the emission spectrum of the fluorophore. Imaging lenses and digital cameras are used to produce the final image [20–22].
Indocyanine green dye (ICG) was developed for near‐infrared (NIR) photography by Kodak Research Laboratories in 1955 and introduced for clinical use in 1956. Several clinical applications comprised the use of ICG, such as cirrhotic liver resection.
New successful applications of ICG were very recently published. For example, the use of this dye for assistance during a hepatic metastasectomy allows to identify superficially located colorectal liver metastases and in some patients it was possible to localize small lesions otherwise undetectable by typical procedures.
ICG is recognized to be relatively free of adverse effects when injected into the bloodstream and has been used in veterinary medicine extensively. Once excited with a specific wavelength of light, ICG becomes fluorescent, and this phenomenon can be detected using specific filter scopes and cameras, and then displayed on a screen. Some specific areas with ICG accumulating abilities can be seen, which would not occur with a normal white light endoscopic imaging system. ICG rapidly binds to plasma proteins after its intravascular injection, resulting in minimal leakage to the interstitial compartment.
The major limitation in FIGS is the availability of clinically approved fluorescent dyes. Indocyanine Green has been widely used as a nonspecific agent to detect sentinel lymph nodes (SLN) during surgery.
ICG‐NIR is classified as a nontargeted dye. This means that following administration, the pharmacokinetics of the molecule are known in detail, and this defines whether a probe is a good imaging agent for the observation of a given target according to its biodistribution, excretion pathways, accumulation patterns, etc. In general, nontargeted probes show poor differentiation between malignant and healthy tissue boundaries. A major area of research in fluorescence imaging is the identification and approval of new targeted dyes, which will offer better tissue differentiation at a reasonable cost.
Future trends in fluorescence imaging will depend on the research and development of antibody binding and specific tissue‐binding dye abilities. This step will expand the opportunities for targeted oncologic surgery and specific planning for complete tissue resection. Most of these specific fluorophore molecules rely on NIR fluorescence properties, and their ability to bind to receptors on specific cell membranes or extracellular matrix enzymes. They can efficiently recognize the intended molecular target and selectively accumulate on the malignancy sites, thereby rendering dramatic improvements in signal‐to‐background ratio over nontargeted probes.
The complete system can be switched from standard white light mode to NIR/ICG mode, and vice versa, simply by foot‐pedal control, or with camera head buttons on the new generation 4K NIR/ICG cameras (RUBINA® – KARL STORZ). When used in NIR/ICG fluorescence mode, the technology can either offer images in blue or green, which enhances the image in highly perfused and fluorescent areas (blue mode), to more intense fluorescence and detailed delineation against surrounding tissue (green mode) [20–22]. RUBINA cameras (KARL STORZ) present also other NIR/ICG advantages such as Monochromatic Fluorescence which enables black and white imaging mode for better operating contrast, sharper edges, and brightness (Figure 3.9a).
Videoendoscopic oncologic surgery can benefit from NIR technology, since ICG is used to map neoplastic tissues and their lymphatic drainage. Consequently, mapped lymph nodes are surgically removed, allowing for subsequent histopathological analysis. Sentinel lymph node mapping is now enhanced with the use of the Fluorescence Intensity Map, since it achieves an improved distinction between lymph nodes and surrounding lymphatic pathways.
The recent introduction of Intensity Map enables the surgeon to interpret the grade of fluorescence displayed on the screen and correlate that with an
